MATLAB Array and String Functions

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What does the function `diag(v)` do in MATLAB?

Creates a vector equal to the main diagonal of matrix v

Converts a vector into a column matrix

Generates a square matrix filled with ones

Makes a square matrix of zeroes with vector in the main diagonal (correct)

How is a string created in MATLAB?

By defining a vector of characters using `char` function

By using double quotes around the characters

By concatenating strings with the plus operator

By typing characters within single quotes (correct)

When strings are indexed in MATLAB, what is true about reading by index?

Strings are indexed only from the end towards the beginning

Indexes for strings start from zero by default

Strings cannot be indexed; they are treated as a single unit

Indexing retrieves characters based on their position in the string (correct)

What would be the result of the command `word(1) = 'v';` if `word` is initially set to 'dale'?

'd' will be replaced with 'v', resulting in 'vale' Signup and view all the answers

How can you insert characters in a string variable in MATLAB?

Use indexing to specify where to add new characters Signup and view all the answers

What is a consequence of attempting to vertically concatenate strings of different lengths in MATLAB?

An error will occur due to dimension inconsistency. Signup and view all the answers

How does MATLAB handle string arrays when using the char function?

It pads each string to the length of the longest string. Signup and view all the answers

Given the command `names = [ 'Greg'; 'Jon' ]`, what is the expected result?

An error due to inconsistent row lengths. Signup and view all the answers

What is the output of the command `size(question)` if `question` is assigned using the char function to hold three lines of varying lengths?

3xM array where M equals the longest string's length. Signup and view all the answers

When using `char('string 1', 'string 2')`, what is the primary purpose of this function?

To ensure all strings have equal lengths by adding spaces. Signup and view all the answers

Study Notes

Built-in Functions for Handling Arrays

diag(v) creates a square matrix with zeroes, except for the main diagonal which is populated by the elements of vector v.
diag(A) creates a vector containing the elements of the main diagonal of matrix A.
For more array handling functions, navigate through the help icon in MATLAB: MATLAB -> MATLAB Functions -> By Category -> Matrices and Arrays.

Strings

A string is an array of characters.
Strings in MATLAB are used for:
- Displaying text output
- Specifying plot formatting
- Inputting arguments for functions
- Text input from user or data files
Strings are created by typing characters within single quotes ('). Other programming languages typically use quotation marks (").
Text color changes to maroon when typing the first single quote and purple when typing the last single quote.

Strings: Characters & Symbols

Strings can contain letters, digits, symbols, and spaces.
Single quotes within a string can be represented using two consecutive single quotes (')
Examples of strings: 'ad ef', '3%fr2', 'edcba:21!', 'MATLAB'.

String Variables

Strings can be assigned to variables like numbers.
Example:
- name = 'Sting', police = 'New York''s finest'.

String Variables: Storage & Indexing

Numbers in strings are stored as an array.
A one-line string is a row vector, with the number of elements equaling the number of characters in the string.
Example:
- name = 'Howard the Duck' has 15 characters and thus a size of 1x15.
Strings can be indexed and manipulated similarly to vectors and matrices. Elements can be read, written, and deleted by index.

String Variables: Example Operations

Example:
- word = 'dale', word(1) = 'v' changes the word to vale.
- word(end) = [] removes the last character e from vale resulting in val.
- word(end+1:end+3) = 'ley' adds ley to val, making it valley.

Multi-line Strings

MATLAB stores multiline strings as arrays.
Each line must have the same number of characters (columns).
If lines have a different number of characters, MATLAB throws an error when combining them in a vertical array (names = ['Greg'; 'Jon']).
To avoid errors, manually add spaces (or other characters) to make all lines the same length.
- Example: names = ['Greg'; 'Jon '].

char Function

char function overcomes the need for manual padding by adding enough spaces to each line on the right side to ensure all lines have the same number of characters.
- Example: char('string 1', 'string 2', 'string 3').

`char` Function: Example Usage

Example:
- question=char('Romeo, Romeo,', 'Wherefore art thou', 'Romeo?') creates a multi-line string, where each line has exactly 18 characters due to the added space characters.

Matrices: Appending Elements

To append matrices, the dimensions must match:
- Adding a matrix to the right side of another matrix requires the same number of rows for both matrices.
- Adding a matrix to the bottom of another matrix requires the same number of columns for both matrices.

Matrices: Appending Example

Examples:
- Z=[A2 B2] appends matrix B2 to the right of A2. Both have the same number of rows.
- Z=[A2; C2] appends matrix C2 below matrix A2. Both have the same number of columns.
- Z=[A2; B2] throws an error because A2 and B2 have different number of columns.

Matrix: Unassigned Elements

Unassigned elements in matrices are set to zero by default.
Example:
- Matrix BG initially has only a few elements populated. When a new element BG(3,4) = 15 is assigned, the other elements retain their default value of zero.

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Description

This quiz covers built-in functions in MATLAB for handling arrays and strings. It focuses on creating square matrices, extracting main diagonals, and understanding string functionalities. Test your knowledge on these essential MATLAB concepts!

MATLAB Array and String Functions

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Questions and Answers